South Korea's Samsung did not release its star phone, the Galaxy S8, instead launched a new tablet, the Samsung Galaxy Tab S3, with a 9.7-inches screen and a 6,000 mAh battery that allows 12 hours of video playback.
It also presented a new version of virtual reality glasses, Samsung Gear VR and the Galaxy Book, a mixture of tablet and computer that will be on sale in two different sizes, with a 12-inches screen or a 10.6-inches screen.
Chinese companies including Huawei, ZTE, Lenovo and TCL also released their new devices during the weekend.
All devices will be displayed from Monday to Thursday at the Fira Gran Via venue in Barcelona during the MWC.
Being the world's most important mobile industry event, this year's MWC is expected to gather 2,200 exhibitors, 101,000 trade visitors from 200 countries and regions.